An ink drop detector includes a sensing target which is imparted with an electrical stimulus when struck by at least one ink drop burst which has been ejected from an ink drop generator. The detector also includes electronics coupled to the sensing target which characterize the electrical stimulus in terms of a mathematical phase. Methods for analyzing ink ejected from an ink drop generator, and a method for optimizing ink drop generator firing frequency are also provided.
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19. A method for analyzing ink ejected from an ink drop generator, comprising:
generating an electrical stimulus on an ink drop detector target by firing at least one ink droplet onto the target; calculating a mathematical phase based on the electrical stimulus; and determining an ink system characteristic based on the mathematical phase.
1. An ink drop detector, comprising:
a sensing target which is imparted with an electrical stimulus when struck by at least one ink drop burst which has been ejected from an ink drop generator; and electronics coupled to the sensing target which characterize the electrical stimulus in terms of a mathematical phase, wherein the mathematical phase indicates at least one ink system characteristic.
40. A method for analyzing ink ejected from an ink drop generator, comprising:
generating an electrical stimulus on an ink drop detector target by firing at least one ink droplet onto the target; calculating a mathematical phase based on the electrical stimulus; calculating a mathematical vector based on the electrical stimulus; determining an ink system characteristic based on both the mathematical phase and the mathematical vector.
54. A method for optimizing ink drop generator firing frequency, comprising:
generating a series of electrical stimuli by firing a series of ink droplets or a series of ink drop bursts onto an electrostatic drop detector target at a known firing frequency; calculating a mathematical phase for each electrical stimulus; calculating a mathematical vector for each electrical stimulus; determining a statistical ink drop weight for ink drops fired at the known firing frequency based on the mathematical phase and mathematical vector associated with each stimulus; storing the statistical ink drop weight with corresponding known firing frequency in a dataset for further examination; changing the known firing frequency to a different known firing frequency; repeating the preceding steps until a desired firing frequency range is covered; examining the stored dataset comprising pairs of ink drop weights and known firing frequencies to determine a pivotal firing frequency before which the ink drop weight starts to decline enough to affect image quality, setting the firing frequency to the pivotal firing frequency.
2. The ink drop detector of
circuitry coupled to the sensing target to produce a filtered and amplified signal from the electrical stimulus; and a processor coupled to the circuitry which characterizes the filtered and amplified signal in terms of a mathematical phase.
4. The ink drop detector of
5. The ink drop detector of
6. The ink drop detector of
circuitry coupled to the sensing target to produce a filtered and amplified signal from the electrical stimulus; and a processor coupled to the circuitry which characterizes the filtered and amplified signal in terms of a mathematical phase and in terms of a mathematical vector.
7. The ink drop detector of
the mathematical phase indicates at least one phase-based ink system characteristic; and the mathematical vector indicates at least one vector-based ink system characteristic.
8. The ink drop detector of
9. The ink drop detector of
10. The ink drop detector of
11. The ink drop detector of
12. The ink drop detector of
13. The ink drop detector of
14. The ink drop detector of
15. The ink drop detector of
17. The ink drop detector of
18. The ink drop detector of
20. The method of
21. The method of
22. The method of
comparing the ink system characteristic to known ink system characteristics; and adjusting parameters of the ink drop generator to optimize image quality.
23. The method of
24. The method of
25. The method of
26. The method of
27. The method of
calculating a mathematical vector based on the electrical stimulus; and determining an ink system characteristic based on the mathematical vector.
28. The method of
29. The method of
30. The method of
using the determined ink drop size to make drop-based ink usage measurements more accurate.
31. The method of
32. The method of
comparing the ink system characteristic to known ink system characteristics; and adjusting parameters of the ink drop generator to optimize image quality.
33. The method of
34. The method of
35. The method of
36. The method of
37. The method of
38. The method of
sampling the electrical stimulus at substantially equal intervals; and performing digital signal processing based on the sampling.
39. The method of
sampling the electrical stimulus at non-equal intervals; and performing digital signal processing based on the sampling.
41. The method of
42. The method of
43. The method of
44. The method of
45. The method of
46. The method of
comparing the ink system characteristic to known ink system characteristics; and adjusting parameters of the ink drop generator to optimize image quality.
47. The method of
48. The method of
49. The method of
50. The method of
51. The method of
52. The method of
sampling the electrical stimulus at substantially equal intervals; wherein calculating a mathematical phase based on the electrical stimulus comprises performing digital signal processing based on the sampling; and wherein calculating a mathematical vector based on the electrical stimulus comprises performing digital signal processing based on the sampling.
53. The method of
sampling the electrical stimulus at non-equal intervals; wherein calculating a mathematical phase based on the electrical stimulus comprises performing digital signal processing based on the sampling; and wherein calculating a mathematical vector based on the electrical stimulus comprises performing digital signal processing based on the sampling.
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Printing mechanisms, such as inkjet printers or plotters, often include an inkjet printhead which is capable of forming an image on many different types of media. The inkjet printhead ejects droplets of colored ink through a plurality of orifices and onto a given media as the media is advanced through a printzone. The printzone is defined by a plane created by the printhead orifices and any scanning or reciprocating movement the printhead may have back-and-forth and perpendicular to the movement of the media. Conventional methods for expelling ink from the printhead orifices, or nozzles, include piezo-electric and thermal techniques which are well-known to those skilled in the art. For instance, two earlier thermal ink ejection mechanisms are shown in U.S. Pat. Nos. 5,278,584 and 4,683,481, both assigned to the present assignee, the Hewlett-Packard Company.
In a thermal inkjet system, a barrier layer containing ink channels and vaporization chambers is located between a nozzle orifice plate and a substrate layer. This substrate layer typically contains columnar arrays of heater elements, such as resistors, which are individually addressable and energized to heat ink within the vaporization chambers. The energy which is applied to a given resistor to heat the ink to the point of drop ejection is referred to as the turn-on energy. Upon heating, an ink droplet is ejected from a nozzle associated with the energized resistor.
A printing mechanism may have one or more inkjet printheads, corresponding to one or more colors, or "process colors" as they are referred to in the art. For example, a typical inkjet printing system may have a single printhead with only black ink; or the system may have four printheads, one each with black, cyan, magenta, and yellow inks; or the system may have three printheads, one each with cyan, magenta, and yellow inks. Of course, there are many more combinations and quantities of possible printheads in inkjet printing systems, including seven and eight ink/printhead systems.
Each process color ink is ejected onto the print media in such a way that size, relative position of the ink drops, and color of a small, discreet of process inks are integrated by the naturally occurring visual response of the human eye to produce the effect of a large colorspace with millions of discernable colors and the effect of a nearly continuous tone. In fact, when these imaging techniques are performed properly by those skilled in the art, near-photographic quality images can be obtained on a variety of print media using only three to eight colors of ink.
This high level of image quality depends on many factors, several of which include: consistent and small ink drop size, consistent ink drop trajectory printhead nozzle to the print media, and extremely reliable inkjet printhead nozzles which do not clog. Ink drop detectors may be employed in a printing mechanism to monitor nozzles for clogging, but it would be useful to also monitor drop size and trajectory. More specifically, it would be beneficial to be able to measure the numerous factors which affect ink drop size and trajectory.
Therefore, it is desirable to have a method and mechanism for effectively, efficiently, and economically measuring ink system characteristics which affect ink drop size and trajectory, such as viscosity, electrical conductivity, dye load, surface tension, drop firing turn-on energy, drop velocity, and ink age.
While it is apparent that the printer components may vary from model to model, the typical inkjet printer 20 includes printer control electronics, illustrated schematically as a controller 22 that receives instructions from a host device, such as a computer or personal digital assistant (PDA) (not shown). Printer host devices, such as computers and PDA's are well known to those skilled in the art.
The typical inkjet printer 20 will include an ink drop generator 24 which is capable of ejecting drops of ink onto a print media. Ink drop generator 24 may be configured to work with pigment based inks or dye based inks. The dye and pigment based inks may be of different colors, such as, for example, black, cyan, magenta, or yellow. The printing mechanism 20 may contain a single drop generator 24 for use with a single color of ink; multiple ink drop generators 24, each for use with a single color of ink; a single drop generator 24 for use with multiple colors of ink; multiple drop generators 24, each for use with multiple colors of ink; or a combination of drop generators 24 where at least one is for use with a single color of ink and at least one is for use with multiple colors of ink. It is apparent that other types of inks may also be used in the ink drop generators 24, such as paraffin-based inks, as well as hybrid or composite inks having both dye and pigment characteristics. A printing mechanism 20 may have replaceable ink drop generators 24 where each drop generator 24 has a reservoir that carries the entire ink supply as the drop generator 24 reciprocates over the print media. As used herein, the term "ink drop generator" may also refer to an "off-axis" ink delivery system, having main stationary reservoirs (not shown) for each ink (black, cyan, magenta, yellow, or other colors depending on the number of inks in the system) located in an ink supply region. In an off-axis system, the ink drop generators 24 may be replenished by ink conveyed through a flexible tubing system from the stationary main reservoirs which are located "off-axis" from the path of ink drop generator 24 travel, so only a small ink supply is propelled while printing. Other ink delivery or fluid delivery systems may also employ the systems described herein, such as replaceable ink supplies which attach onto ink drop generators having permanent or semi-permanent print heads.
Each ink drop generator 24 has an orifice plate with a plurality of nozzles formed therethrough in a manner well known to those skilled in the art. The nozzles of each ink drop generator 24 are typically formed in at least one, but typically two columnar arrays along the orifice plate. Thus, the term "columnar" as used herein may be interpreted as "nearly columnar" or substantially columnar, and may include nozzle arrangements slightly offset from one another, for example, in a zigzag arrangement. The ink drop generator 24 is illustrated as having a thermal inkjet printhead 26, although other types of printheads, or ink drop generators may be used, such as piezoelectric printheads. The thermal printhead 26 typically includes a plurality of resistors which are associated with the nozzles. Upon energizing a selected resistor, a bubble of gas is formed which ejects a droplet 30 of ink from the nozzle. The printhead 26 resistors are selectively energized in response to firing command control signals 28 delivered from the controller 22 to the ink drop generator 24.
The target 34 may also be coupled to filtering electronics and an amplifier which are part of electronics 36. The charged ink droplets 30 induce an electrical stimulus, such as a current spike, when they contact the target 34, and this current spike may be sensed and amplified by the electronics 36. For efficiency, a grouping of printhead 26 nozzles are typically fired together in one ink burst 40 over the target 34. Although ink burst 40 is illustrated as a group of three ink droplets 30 in
As illustrated in
and where M equals the number of sample data points taken in the burst. In the example illustrated in
The EDD Score 46 and the EDD Phase 48 associated with a particular ink drop burst 40 can be correlated with particular characteristics of an ink system. As
As
EDD Score 46 and an EDD Phase 48 may be calculated as indicated above for an ink droplet 30 or an ink burst 40 containing multiple droplets 30. EDD Score 46 has a quantifiable relationship with ink conductivity 54 and ink drop size 56. EDD Phase 48 has a quantifiable relationship with turn-on-energy (TOE) 58 and ink drop velocity 60. Ink system characteristics such as break-off point (BOP) 64, as well as ink viscosity, surface tension, dye load, and ink age, have a quantifiable relationship with both EDD Score 46 and EDD Phase 48. Given these various relationships which exist between the ink system characteristics, and which may be predetermined, a printing mechanism 20 may be configured to detect and determine changes in the ink properties or changes in the ink system characteristics and make adjustments to ink drop generator 24 firing voltages, printing speeds (determined among other things by printhead 26 firing frequencies and ink drop generator 24 velocity in a reciprocating ink drop generator 24 system), ink drop size, ink drop placement, and other image quality attributes within the controller's 22 control to optimize print quality for the type of ink being used.
As the graph in
However, using the embodiments described herein, and their equivalents, firing frequency 104 may now be varied and drop size 56 and drop weight 102 calculated automatically at several frequencies.
Ink usage measurements can also benefit from the ability of a printer 20 to accurately calculate ink drop size 56. Previous attempts to track ink usage from a given ink drop generator 24 have been based on drop counting techniques. At first, these drop counting techniques were simply keyed off of the controller's 22 firing command signals 28. Each time a nozzle was told to fire, a counter was incremented inside of the controller 22. Based on a knowledge of an ink drop generator's 24 starting ink volume, an assumption regarding the average drop size, and an assumption that when a nozzle was told to fire that it actually did fire, an estimate of ink usage could be arrived at. Unfortunately, nozzles do not always fire due to resistor failure or clogging, and drop size may significantly vary from one ink formulation to another, from one ink drop generator 24 to another, and by ink manufacturer. This results in an inaccurate ink usage measurement.
An different ink usage measurement system relied on a periodic check to determine if in fact the printhead 26 nozzles were firing. This was accomplished through the use of a low cost ink drop detector, such as the one employed in U.S. Pat. No. 6,086,190. A sequence of firing command control signals 28 were sent from the controller 22 to the ink drop generator 24 to cause the printhead 26 nozzles to fire ink droplets. The controller 22 was able to track if an ink droplet was ejected from each printhead 26 nozzle as requested by looking for corresponding signals from the ink drop detector. As a result, the ink usage measurement is more accurate in this type of system because non-firing nozzles were not counted. Unfortunately, this type of measurement still takes into account an assumption of ink drop size. Ink drop size, however, may vary and the result is a less than accurate ink usage measurement.
Using the embodiments and their equivalents disclosed herein, it is possible to not only know whether a printhead 26 nozzle is functioning, but also to know what ink drop size is being ejected from each nozzle on the printhead. By periodically updating this information, a highly accurate ink usage measurement may be made tracking the actual volume of ink which is ejected from an ink drop generator 24. Operators of a printer 20 may then either track their ink usage or receive accurate warning that they will soon need to replace the ink supplies in the printer 20.
An ink drop detector 32 may be used to determine ink system characteristics, enabling a printing mechanism to reliably use ink drop detection readings to provide users with consistent, high-quality, and economical inkjet output despite printheads 26 which may clog over time and despite ink formulations which may change, age, or are supplied from another manufacturer. In discussing various embodiments of ink system characteristic identification, various benefits have been noted above.
Although the ink system characteristics described herein include ink conductivity, ink drop size, ink drop weight, ink drop velocity, turn-on-energy, break-off-point, viscosity, dye-load, surface tension, and age of the ink, it is apparent that other ink system characteristics may be determined with relation to EDD Score, EDD Phase, or EDD Score in conjunction with EDD Phase. Such ink system characteristics are deemed to be within the scope of the claims below. Additionally, it is apparent that a variety of other structurally and functionally equivalent modifications and substitutions may be made to determine ink system characteristics according to the concepts covered herein depending upon the particular implementation, while still falling within the scope of the claims below.
Su, Wen-Li, Therien, Patrick J.
Patent | Priority | Assignee | Title |
10556424, | Jan 24 2017 | BOE TECHNOLOGY GROUP CO , LTD | Apparatus and method for detecting the volume of a liquid drop, and method for adjusting the volume of a liquid drop |
11794472, | Sep 26 2019 | Videojet Technologies Inc | Method and apparatus for continuous inkjet printing |
7281778, | Mar 15 2004 | FUJIFILM DIMATIX, INC | High frequency droplet ejection device and method |
7673976, | Sep 16 2005 | Eastman Kodak Company | Continuous ink jet apparatus and method using a plurality of break-off times |
7938502, | Sep 19 2007 | Seiko Epson Corporation | Flushing method for fluid ejecting device and fluid ejecting device |
7946670, | Feb 13 2002 | Silverbrook Research Pty LTD | Inkjet printer with a replaceable quality-assured ink cartridge |
7988247, | Jan 11 2007 | FUJIFILM DIMATIX, INC | Ejection of drops having variable drop size from an ink jet printer |
8057006, | Oct 24 2007 | Hewlett-Packard Development Company, L.P. | Fluid ejection device |
8087740, | Sep 16 2005 | Eastman Kodak Company | Continuous ink jet apparatus and method using a plurality of break-off times |
8294946, | Jun 12 2006 | Hewlett-Packard Development Company, L.P.; Hewlett-Packard Development | Printer |
8388098, | Jul 23 2008 | Hewlett-Packard Development Company, L.P. | Printing orifice health detection device |
8393702, | Dec 10 2009 | FUJIFILM Corporation | Separation of drive pulses for fluid ejector |
8459768, | Mar 15 2004 | FUJIFILM Dimatix, Inc. | High frequency droplet ejection device and method |
8474938, | Oct 24 2007 | Hewlett-Packard Development Company, L.P. | Replaceable printing component |
8491076, | Mar 15 2004 | FUJIFILM DIMATIX, INC | Fluid droplet ejection devices and methods |
8708441, | Dec 30 2004 | FUJIFILM DIMATIX, INC | Ink jet printing |
9381740, | Dec 30 2004 | FUJIFILM Dimatix, Inc. | Ink jet printing |
Patent | Priority | Assignee | Title |
6056386, | Oct 02 1995 | Canon Kabushiki Kaisha | Testing for normal print discharge |
6086190, | Oct 07 1997 | HEWLETT-PACKARD DEVELOPMENT COMPANY, L P | Low cost ink drop detector |
6322193, | Oct 23 1998 | Industrial Technology Research Institute | Method and apparatus for measuring the droplet frequency response of an ink jet printhead |
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